>I can’t decode French elitism.
It is a clear case of "langue-dans-la-joue"
(or is it "langue-dans-la-fesse"?).
It would not be "langue-dans-la-fesse" for sure, even if this expression is very humoristic itself! Tongue in cheek can be said "pince-sans-rire" : https://fr.wikipedia.org/wiki/Pince-sans-rire